Method of making heat-exchange unit



Jan. 25, 1949.

N. T. MCKEE METHOD OF MAKING HEAT-EXCHANGE UNIT Filed May 19, 1945 INVENTOR. Neal T McKee ATTORNEYS Patented Jan. 25, 1949 METHOD OF MAKING HEAT-EXCHANGE UNIT Neal T. McKee, Bronxville, N. Y., assignor to The Superheater Company, New York, N. Y., a corporation of Delaware Application May 19, 1945, Serial No. 594,740

1 Claim. 1

This invention relates to a, method of making a heat-exchange unit, more particularly, a heat exchanger formed by a tube having a substantially continuous helical fin thereon.

An object of this invention is to provide a meth d of making an extremely eificient and practical heat-exchange unit.

This invention accordingly consists in the several steps and relation and order of each of the same to one or more of the others, all as will be illustratively described herein, and the scope of the application of which will be indicated in the following claim.

In the drawing:

Figure 1 is a view showing the production of a heat exchanger which constitutes one embodiment of the invention;

Figure 2 is a side elevation of a single fin element in the form in which it appears before assembly to the tube; and

Figures 3 and 4 are respectively side and front elevations of the fin while the fin is in the form of a disc.

In the heat-exchange art it is desirable to provide good heat transfer between the fin assembly and the tube and also between the fluids respectively making contact with the tube and the fins. Thus, the fins should be so shaped that the fluid such as air which makes contact with them will pass the fins eificiently, and the fins must be attached to the tube through a zone of sufiicient cross-section for the proper heat transfer to take place between the fins and the tube. In the manufacture oi heat-exchange units the proper positioning and attaching of the fins is at times a tedious and expensive operation. Under some circumstances, it is highly desirable and even necessary to provide an actual metal bond between the fin and the tube, and this bond should be produced in an efiicient and dependable manner. If the procedure is not dependable there may be a portion of the fin which is not properly bonded to the tube so that that portion of the fin produces no real useful effect. That is, the heat-exchange relationship between the tube and its fluid may be satisfactory, and similarly the heat-exchange relationship between the fin and its fluid may be quite satisfactory, but if the bond between the fin and the tube has a gap in it, the portion of the fin opposite this gap will be practically useless.

It is also desirable to provide a fin assembly of such structure that the fluid passing around it will make thorough contact with all of the fin surface, Thus, if the fin is of such contour that the fluid passes rapidly over one portion of it, but yet the fluid is relatively stationary at another portion of it, the proper heat-exchange relationship will not exist. It is an object of the present invention to avoid the disadvantages of the prior art and to produce a heat-exchange unit which is efiicient and dependable in use and which may be manufactured economically and by the use of practical devices.

Referring to Figure 1 of the drawing, a tube 2 is provided with a spiral or helical fin assembly formed by a plurality of individual fins 4. Each fin 4 has a fin portion 6 and a collar portion 8 and the collar portion is welded to the tube along two spiral lines or zones indicated at it and I2. Fins 4 are of the type shown in Figure 2 and each is produced by first making a disc of the type shown in Figures 3 and 4. Referring particularly to Figures 3 and 4, a circular disc is formed having a central opening surrounded by a collar, and this disc is out along a radius at 14. After being cut, the radial meeting edges of the disc at it are offset to the shape of a helix as in Figure 2.

These fins may be threaded onto the tube at one end of the tube, or they may be sprung apart and slipped over the tube from the side. That is, the two ends of the helical fin may be spread apart, as by pulling the ends out and by temporarily increasing the pitch of the spiral. After assembly on the tube the fins are placed in a continuous spiral with the lead end of one fin abutting the trailin end of the next adjacent fin. The tube is then fed through a pair of Welding roller electrodes l6 and [8 which have their axes offset angularly to correspond with the pitch of the spiral. The lower electrode l8 produces the line weld I!) while upper electrode I6 produces the line weld [2. These welds are of the overlapping, spot-weld type, and they provide an excellent heat-exchange bond between the tube and the fin. The tube is fed between the electrodes by rotating the electrodes, and guide means, not shown, may be provided to align each fin with electrode l8 as it approaches the electrode. The fins are so arranged that the electrodes roll from the trailing end of one fin onto the leading end of the next fin. The rotation of the welding rollers may serve also to feed the tube longitudinally so that the fins may be successively welded in spiral relationship, one to the other.

In use the fin assembly is sturdy and is not easily deformed; furthermore, air or other fluid passing around the fin assembly comes into intimate heat-exchange relationship with both sides of all ortions of the fins. The breaks or gaps between the leading and trailing edges of the successive fins in the fin assembly give unusual advantages. For example, the fin assembly is not subjected to undue physical stresses during rapid and extended changes in temperature. Furthermore, the fluid passing through these gaps affects fiuid flow in such a manner as to enhance the heat transfer between the fluid and the fin.

As many possible embodiments may be made of the mechanical features of the above invention and as the art herein described might be varied in various parts, all without departing from the scope of the invention, it is to be understood that all matter hereinabove set forth, or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

I claim:

In the art of making a heat exchanger by attaching to a metal tube a series of helical metal fins each of which is formed from a. discwithsa central opening, and. a collar therearound, said fins being mounted around said tube with their collars in engagement with said tube and in abutment with the cellars of the adjacent fins, and each of which fins is slitted radially with its radial edges offset into abutment with 4 the edges of the adjacent fins to form a substantially continuous helical fin assembly, the method of securing said fins to said tube which comprises placing a pair of welding electrodes in engagement with said collars at opposite points in the same axial plane and in the same transverseplane, feeding said tube and fins past REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number- Name Date 2,021,117 Lucke Nov. 12, 1935 2,161,898 Led-better June 13, 1939 226L136 Brown -i Nov. 4, 1941 2,344,790 Schryoer Mar. 21, 1944 

